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981.
Keun Joo Choi Sang Goo Kim Chang Won Kim Jae Kwang Park 《Korean Journal of Chemical Engineering》2006,23(3):399-408
Removal efficiencies of endocrine disrupting chemicals (EDCs), bisphenol A and nonylphenol, during various types of water
treatment processes were evaluated extensively using laboratory- and pilot-scale experiments. The specific processes of interest
were coagulation/flocculation sedimentation/filtration (conventional water treatment process), powdered activated carbon (PAC),
granular activated carbon (GAC), ozonation and chlorination. Batch sorption tests, coagulation tests, and ozone oxidation
tests were also performed at higher concentrations with 14 EDCs including bisphenol A. The conventional water treatment process
had very low removal efficiencies (0 to 7%) for all the EDCs except DEHP, DBP and DEP that were removed by 53%, 49%, and 46%,
respectively. Ozonation at 1 mgO3/ L removed 60% of bisphenol A and 89% of nonylphenol, while chlorination at 1 mg/L removed 58% and 5%, respectively. When
ozone and chlorine doses were 4 and 5 mg/L, respectively, both EDCs were not detected. PAC removal efficiencies ranged from
15% to 40% at 3 to 10 mg/L of PAC with a contact time of 15 minutes. In the high concentration batch sorption tests, EDC removal
efficiencies by PAC were closely related to octanol-water partition coefficient (Kow). GAC adsorption was very effective water treatment process. The type and service time of GAC did not affect EDC removal
efficiencies. The combination of ozonation and GAC in series appears to remove EDCs effectively to safe levels while conventional
water treatment could not. 相似文献
982.
Multiwalled carbon nanotubes (MWNT) were functionalized with segmented polyurethanes (PU) by the “grafting to” approach. Raman and X‐ray photoelectron spectroscopy (XPS) spectra show that the sidewalls of MWNTs have been functionalized with acid treatment, and the amount of COOH increases with increasing acid treatment time. FTIR and X‐ray diffraction (XRD) spectra confirm that PU is covalently attached to the sidewalls of MWNTs by esterification reaction. Similar to the parent PU, the functionalized carbon nanotube samples are soluble in highly polar solvents, such as dimethyl sulfoxide (DMSO) and N,N‐dimethylformamide (DMF). The functionalized acid amount and the grafted PU amount were determined by thermogravimetric analyses (TGA). Comparative studies, based on SEM images between the PU‐functionalized and chemically defunctionalized MWNT samples, also reveal the covalent coating character. Dynamic mechanical analysis (DMA) of nanocomposite films prepared from PU and PU‐functionalized MWNTs show enhanced mechanical properties and increased soft segment Tg. Tensile properties indicate that PU‐functionalized MWNTs are effective reinforcing fillers for the polyurethane matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
983.
This work describes initial efforts to incorporate affinity ligands within an environmentally responsive hydrogel. Metal affinity ligands were chosen as model affinity groups and thermally responsive N‐isopropyl acrylamide/acrylamide copolymers were used as the base hydrogels. The ? NH2 group of the acrylamide serves as a reactive group for functionalization with metal affinity ligands. The gels were synthesized by free radical polymerization and Cu2+ was bound to the gel via 1,4‐butanediol diglycidyl ether (BDE) as a linker and iminodiacetic acid (IDA) as a chelating ligand. The base acrylamide gels were also functionalized with metal affinity ligands to allow for comparison with thermally responsive affinity gels. The results show the effectiveness of this technique for both these types of gels, and an improved method to immobilize metal affinity groups on to thermally sensitive N‐isopropyl acrylamide gels was also developed. It was seen that the yields for the reaction with BDE decreased with increased reaction time in both kinds of gels, whereas reaction with IDA showed a decrease in yields with increase in temperature for N‐isoporpyl acrylamide gels and increase in yields for acrylamide gels. Further techniques were developed to overcome diffusional resistances and stresses in the thermally responsive N‐isopropyl acrylamide gels so as to improve the distribution of Cu2+ ions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
984.
Olli-Pekka Tossavainen Marko Vauhkonen Kyung Youn Kim 《Chemical engineering science》2006,61(23):7717-7729
Sedimentation monitoring is widely used to control and optimize industrial processes. In this paper we propose a novel computational method for sedimentation monitoring using electrical impedance tomography (EIT). EIT measurements consist of electric current and voltage measurements that are made on the surface of the sedimentation tank and therefore they do not interfere with the sedimentation process. The proposed computational method is based on shape estimation and state estimation formulation of the EIT problem. The sedimentation is parameterized by the locations of the phase interfaces and conductivities of the phase layers. Three different evolution models for the state parameters are considered and the state estimates are computed using the extended Kalman filter algorithm. The performance of the method and the models are evaluated using simulated data from a six electrode EIT measurement configuration. From the results a promising performance of the method can be seen. 相似文献
985.
Young-Bae Park Yong-Woo Choi Xiaodong Li 《Journal of Materials Science: Materials in Electronics》2006,17(1):27-33
Polycrystalline silicon germanium (poly-Si1−xGex) thin films on a-Si film have been deposited by rapid thermal chemical vapor deposition (RTCVD) with SiH4–GeH4–H2. Effect of GeH4/SiH4 and deposition temperature on stoichiometry (x), Si-Ge binding character, composition, hydrogen configuration, crystallinity, preferred orientation, grain size, and surface
roughness of poly-Si1−xGex films has been investigated. Poly-Si1−xGex deposited on the substrate with amorphous silicon buffer layer on oxide shows better crystallinity and contains the less
amount of oxygen than the one deposited directly on the oxide surface. At low temperature region, the Ge–H bond with the small
amount of Si–H2 bond is dominant but all hydrogen bonds are desorbed at high temperature. All films have polycrystalline phase and the grain
size and (111) orientation increased with increasing deposition temperature in which Ge content also increases at the fixed
gas flow rate of GeH4 to total source gas. Poly-Si1−xGex/Si thin film transistors (TFT) are fabricated and hydrogen during post-hydrogenation process preferentially is attached to
Ge dangling bond and the TFT characteristics could be improved. 相似文献
986.
Active damping of rotating composite thin-walled beams using MFC actuators and PVDF sensors 总被引:1,自引:0,他引:1
The object of this research is to enhance the damping performance for vibration suppression of rotating composite thin-walled beams using MFC actuators and PVDF sensors. The formulation is based on single cell composite beam including a warping function, centrifugal force, Coriolis acceleration and piezoelectric effect. Adaptive capability of the beam is acquired through the use of a negative velocity feedback control algorithm. Numerical analysis is performed using finite element method and Newmark time integration method is used to calculate the time response of the model. It is observed that the feedback control gain has an effect on damping performance. The paper continues with an investigation into influences of parameters such as the rotating speed and the fiber orientation in host structures. Also, it is confirmed that effective damping performance is achievable through the suitable arrangement and distributed size of sensor and actuator pair using case study. 相似文献
987.
Nondestructive sensing of a single-carbon fiber reinforced epoxy composites was evaluated by the measurement of electrical resistivity under reversible cyclic loading. For the strain–stress sensing, the strain up to the maximum load of a bare carbon fiber itself is larger than that of carbon fiber composite. As curing temperature increased, apparent modulus up to the maximum load increased and the elapsed time became shorter. Higher residual stress might contribute to the improved interfacial adhesion. The strain up to the maximum load at low temperature was larger than that at higher temperature. The strain of electrodeposition (ED) treated carbon fiber was smaller than that of the untreated carbon fiber composite until the maximum load reached. This could be due to higher apparent modulus of composite based on the improved interfacial shear strength (IFSS). Since the electrical resistivity was responded well quantitatively with various parameters, such as matrix modulus, the fiber surface modification, the electrical resistivity measurement can be a feasible method of nondestructive sensing evaluation for conductive fiber reinforced composites inherently. 相似文献
988.
Kee Bae Park Sang-Do Han Il Jin Kim Jin Suk Wang Young Sung Park 《Materials Science and Engineering: B》2006,130(1-3):158-162
Thick film H2 sensors were fabricated using SnO2 loaded with Ag2O and PdOx. The composition that gave highest sensitivity for H2 was in the wt.% ratio of SnO2:Ag2O:PdOx as 93:5:2. The nano-crystalline powders of SnO2–Ag2O–PdOx composites synthesized by sol–gel method were screen printed on alumina substrates. Fabricated sensors were tested against gases like H2, CH4, C3H8, C2H5OH and SO2. The composite material was found sensitive against H2 at the working temperature 125 °C, with minor interference of other gases. H2 gas as low as 100 ppm can be detected by the present fabricated sensors. It was found that the sensors based on SnO2–Ag2O–PdOx nanocrystalline system exhibited high performance, high selectivity and very short response time to H2 at ppm level. These characteristics make the sensor to be a promising candidate for detecting low concentrations of H2. 相似文献
989.
Yun-Jae Kim Chang-Kyun Oh Man-Sik Myung Jin-Moo Park 《Engineering Fracture Mechanics》2006,73(13):1849-1864
In the present work, fully plastic analyses for notched bars and (plane strain) plates in tension are performed, via finite element (FE) limit analysis based on non-hardening plasticity, from which plastic limit loads and stress fields are determined. Relevant geometric parameters are systematically varied to cover all possible ranges of the notch depth and radius. For the limit loads, it is found that the FE solutions for the notched plate agree well with the existing solution. For the notched bar, however, the FE solutions are found to be significantly different from known solutions, and accordingly the new approximation is given. Regarding fully plastic stress fields, it is found that, for the notched plate, the maximum hydrostatic (mean normal) stress overall occurs in the center of the specimen, which strongly depends on the relative notch depth and the notch radius-to-depth ratio. On the other hand, for the notched bar, the maximum hydrostatic stress can occur in between the center of the specimen and the notch tip. The maximum hydrostatic stress for a given notch depth can occur not for the cracked case, but for the notched case with a certain radius. This is true for both bars and plates. For a given notch radius, on the other hand, the maximum hydrostatic stress increases monotonically with the decreasing notch radius. 相似文献